// UPDATE.cpp

#include <vector>
#include <algorithm>
#include <omp.h>
#include <string>

// Define real type based on precision needs
using Real = double;

// Control parameters (would normally be in a configuration class)
namespace Control {
    extern int NPROC;      // Number of processors
    extern int IOPTMS;     // Simplified mass option flag
}

// Node parameters
namespace Node {
    extern int NOD100;     // Number of null nodes
    extern int NUMNP;      // Total number of nodes
    extern int NBROTN;     // Number of rotational nodes
}

// Error handling function
void ReportError(const std::string& message, int nodeId = -1);

/**
 * @brief Updates body coordinates (LAMBDA-BAR)
 * 
 * This function updates velocities and body coordinates with three strategies:
 * 1) Simplified mass option
 * 2) Standard mass without null nodes
 * 3) Standard mass with null nodes
 * 
 * @param velocities Node velocities (6 components per node)
 * @param globalVel Global velocities (3 components per node)
 * @param bodyLambda Body coordinates (LAMBDA-BAR)
 * @param timeStep Time step size
 * @param errorNode Output: Node causing error (0 if no error)
 * @param nodeMapping Node ID mapping
 * @param nodeOrder Node ordering array
 * @param rotNodes Rotational nodes array
 */
void UpdateBodyCoordinates(
    std::vector<std::array<Real, 6>>& velocities,
    std::vector<std::array<Real, 3>>& globalVel,
    std::vector<Real>& bodyLambda,
    Real timeStep,
    int& errorNode,
    const std::vector<int>& nodeMapping,
    const std::vector<int>& nodeOrder,
    const std::vector<int>& rotNodes)
{
    // Early return if error node is already set
    if (errorNode != 0) return;

    if (Control::IOPTMS != 0) {
        // +---------------------------------------------------------------+
        // Simplified mass option
        // +---------------------------------------------------------------+

        #pragma omp parallel for
        for (int nn = Node::NOD100; nn < Node::NUMNP; ++nn) {
            int node = nodeOrder[nn];
            globalVel[node][0] = velocities[node][3]; // VX = V(4)
            globalVel[node][1] = velocities[node][4]; // VY = V(5)
            globalVel[node][2] = velocities[node][5]; // VZ = V(6)
        }

        // BLAMB update for rotation node list
        int beginIdx = 0;
        int endIdx = Node::NBROTN;
        UpdateMethod1(velocities, globalVel, bodyLambda, timeStep, errorNode, 
                     rotNodes, beginIdx, endIdx);

        if (errorNode != 0) {
            errorNode = nodeMapping[errorNode];
            ReportError("Large rotation for node - will diverge", errorNode);
        }
    }
    else if (Node::NOD100 == 0) {
        // +---------------------------------------------------------------+
        // Standard mass without Null nodes and no adaptive mesh
        // +---------------------------------------------------------------+

        int blockSize = (Node::NUMNP + Control::NPROC - 1) / Control::NPROC;
        std::vector<int> errorNodes(Control::NPROC, 0);

        // Central difference processing
        #pragma omp parallel for
        for (int proc = 0; proc < Control::NPROC; ++proc) {
            int beginIdx = proc * blockSize;
            int endIdx = std::min(Node::NUMNP, (proc + 1) * blockSize);
            UpdateMethod2(velocities, globalVel, bodyLambda, timeStep, 
                         errorNodes[proc], beginIdx, endIdx);
        }

        // Check for errors in any processor
        for (int proc = 0; proc < Control::NPROC; ++proc) {
            if (errorNodes[proc] != 0) {
                errorNode = nodeMapping[errorNodes[proc]];
                ReportError("Large rotation for node - will diverge", errorNode);
                break;
            }
        }
    }
    else {
        // +---------------------------------------------------------------+
        // Standard mass with Null nodes
        // +---------------------------------------------------------------+

        int blockSize = (Node::NUMNP - Node::NOD100 + Control::NPROC - 1) / Control::NPROC;
        std::vector<int> errorNodes(Control::NPROC, 0);

        // Central difference processing
        #pragma omp parallel for
        for (int proc = 0; proc < Control::NPROC; ++proc) {
            int beginIdx = proc * blockSize + Node::NOD100;
            int endIdx = std::min(Node::NUMNP, (proc + 1) * blockSize + Node::NOD100);
            UpdateMethod1(velocities, globalVel, bodyLambda, timeStep, 
                         errorNodes[proc], nodeOrder, beginIdx, endIdx);
        }

        // Check for errors in any processor
        for (int proc = 0; proc < Control::NPROC; ++proc) {
            if (errorNodes[proc] != 0) {
                errorNode = nodeMapping[errorNodes[proc]];
                ReportError("Large rotation for node - will diverge", errorNode);
                break;
            }
        }
    }
}

// Helper functions (would be implemented elsewhere)
void UpdateMethod1(
    const std::vector<std::array<Real, 6>>& velocities,
    std::vector<std::array<Real, 3>>& globalVel,
    std::vector<Real>& bodyLambda,
    Real timeStep,
    int& errorNode,
    const std::vector<int>& nodes,
    int beginIdx,
    int endIdx)
{
    // Implementation of first update method
    // Would include the actual coordinate update logic
}

void UpdateMethod2(
    const std::vector<std::array<Real, 6>>& velocities,
    std::vector<std::array<Real, 3>>& globalVel,
    std::vector<Real>& bodyLambda,
    Real timeStep,
    int& errorNode,
    int beginIdx,
    int endIdx)
{
    // Implementation of second update method
    // Would include the actual coordinate update logic
}

void ReportError(const std::string& message, int nodeId) {
}